In display devices such as liquid crystal displays and organic EL (electroluminescent) displays, pixels are arrayed in high definition on a large-area substrate. In these display devices, the substrate size has been increasing year by year, and as large substrates as, for example, several meters in one side length are used more and more.
With such substrates, for example, in processing or restoring part of pixels after the making of pixel patterns, there is a need for moving the processing apparatus on the substrate to perform processing or restoration on relevant pixels. For this purpose, substrate alignment needs to be done by accurately rotating a substrate placing table, on which the substrate is placed, so that a moving direction of the processing apparatus and a direction of a pixel of the substrate accurately accord with each other.
One of such substrate alignment methods is described in JP H2-283097 A.
This substrate alignment method includes steps of successively observing two references provided on the substrate by a single camera to measure position data, and determining correction amounts from the observed position data and theoretical position data stored in association with the respective references.
According to this substrate alignment method, substrate alignment can be achieved only by comparing observed position data with the stored theoretical position data. Therefore, the substrate alignment can be carried out quickly.